CMake 函数“未在此范围内声明”错误

Question

我是 CMake 的新手，并且一直在阅读博客以使其正常工作。当所有文件都在同一个目录中时，我有一个 cmake 文件工作，但似乎无法让它工作 - 包含目录给我带来了麻烦。在最后一次尝试中，我引用了this 堆栈溢出线程。这是我最接近让它发挥作用的地方。请帮忙。

文件树

$ tree
.
├── CMakeLists.txt
├── include
│   ├── CMakeLists.txt
│   └── math.h
├── src
│   ├── CMakeLists.txt
│   └── math.c
└── testy
    ├── CMakeLists.txt
    └── math.cpp

3 directories, 7 files

CMake 文件

$ more CMakeLists.txt
cmake_minimum_required(VERSION 3.1)
project(iamtesting)
enable_testing()
add_subdirectory(include)
add_subdirectory(src)
add_subdirectory(testy)

$ more include/CMakeLists.txt
add_library(include INTERFACE)
target_include_directories(include INTERFACE ./)

$ more src/CMakeLists.txt
add_library(src STATIC math.c)
target_include_directories(src PUBLIC ./)

$ more testy/CMakeLists.txt
set(TEST_EXE_NAME math)
add_executable(${TEST_EXE_NAME} math.cpp)
target_include_directories(${TEST_EXE_NAME} PUBLIC ./)
target_link_libraries(${TEST_EXE_NAME} src)
add_test(NAME "testDatabase" COMMAND ${TEST_EXE_NAME})

CMake

$ cmake CMakeLists.txt
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/jason/gtest

制作

$ make
Scanning dependencies of target src
[ 25%] Building C object src/CMakeFiles/src.dir/math.c.o
/home/jason/gtest/src/math.c: In function ‘main’:
/home/jason/gtest/src/math.c:5:24: warning: implicit declaration of function ‘sum’ [-Wimplicit-function-declaration]
   printf("10+20=%d\n", sum(10,20));
                        ^~~
[ 50%] Linking C static library libsrc.a
[ 50%] Built target src
Scanning dependencies of target math
[ 75%] Building CXX object testy/CMakeFiles/math.dir/math.cpp.o
In file included from /usr/include/gtest/gtest.h:1874:0,
                 from /home/jason/gtest/testy/math.cpp:1:
/home/jason/gtest/testy/math.cpp: In member function ‘virtual void widget_ok_Test::TestBody()’:
/home/jason/gtest/testy/math.cpp:5:13: error: ‘sum’ was not declared in this scope
   ASSERT_EQ(sum(1, 1), 2);
             ^
/home/jason/gtest/testy/math.cpp:5:3: error: template argument 1 is invalid
   ASSERT_EQ(sum(1, 1), 2);
   ^
testy/CMakeFiles/math.dir/build.make:62: recipe for target 'testy/CMakeFiles/math.dir/math.cpp.o' failed
make[2]: *** [testy/CMakeFiles/math.dir/math.cpp.o] Error 1
CMakeFiles/Makefile2:158: recipe for target 'testy/CMakeFiles/math.dir/all' failed
make[1]: *** [testy/CMakeFiles/math.dir/all] Error 2
Makefile:94: recipe for target 'all' failed
make: *** [all] Error 2

源文件

$ more src/math.c
#include <stdio.h>
#include "math.h"

int main() {
  printf("10+20=%d\n", sum(10,20));
  return 0;
}

int sum(int x, int y) {
    return x + y;
}

$ more include/math.h
#define _MATH_H_

int sum(int, int);

$ more src/math.c
#include <stdio.h>
#include "math.h"

int main() {
  printf("10+20=%d\n", sum(10,20));
  return 0;
}

int sum(int x, int y) {
    return x + y;
}

$ more testy/math.cpp
#include "gtest/gtest.h"
#include "math.h"

TEST(widget, ok) {
  ASSERT_EQ(sum(1, 1), 2);
}

int main(int argc, char **argv) {
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

Answer 1

您的设置存在很多问题：

1. 不需要libInclude（在include/CMakeLists.txt 中定义）。您需要创建一个库 libSrc，其中包含通过 target_include_directories 添加的 include 目录。
2. src 文件夹不得通过target_include_directories 添加，因为它只存储实现您的功能的源文件，并且永远不会在任何地方实际用作#includes。
3. 每个程序中应该只有一个main 函数，所以很可能你应该从src/math.c 中删除main。您应该有一个 main.cpp 用于您的可执行文件，它将链接 libSrc 和一个 main 方法用于您的测试（在您的情况下为 math.cpp，您在此处正确链接了 libSrc）
4. include/math.h 应有适当的include guard